Hand-held or manipulable temperature-sensing devices include at least two general types, the first type having a handle and a shank extending therefrom with a pointed end to be inserted within the mass the temperature of which is to be sensed. Where the mass is of metal, for example, or some other material which cannot be pierced, a surface-temperature-measuring probe is used as a second type of temperature-sensing device. This second type also has a handle and an extending shank, and has some form of blunt end or flat contact face to be pressed against the surface of the object, the temperature of which is to be sensed. Many of the devices of this second type utilize some form of spring which is stressed as the contact face is pressed against the object, the purpose of which is to have the contact face engage the object with a force within a predeterminable range.
A difficulty with this prior art second type of temperature probe is that the person operating the temperature probe cannot be positive that he is maintaining the contact face exactly flat with the object's surface except by touch or sight, and both are difficult where the object surface might be at the bottom of a depression or aperture in the object. Unless this contact face is flat against the object surface, then heat transfer from the object surface to the temperature sensor is greatly impeded, it takes much longer to reach a stable temperature reading on the temperature-sensing apparatus, and the chances are increased of there being an error in the temperature reading obtained by the operator because the temperature sensor did not reach the actual temperature of the object surface, or he did not allow sufficient time for the temperature-sensing apparatus to reach a peak reading.
The prior art has attempted to solve this problem by a structure shown in U.S. Pat. No. 3,282,107, wherein a universal joint is provided between a detector head and a shank with a thermocouple mounted within the detector head. However, then the conductor wires to the thermocouple had to be flexible and, upon repeated flexing, were subject to breakage.
Another attempt to solve generally this same problem was shown in U.S. Pat. No. 3,364,078, which had a flexible mounting of a thermocouple wherein the conductor wires to the thermocouple were resilient and an adjacent cradle block was resiliently supported by a leaf spring, yet, again, one could not be sure that the flat face of the thermocouple would be flat against the object surface.
Still another attempt was made in the prior art to meet this problem in a hand-held thermocouple probe sold by Alnor Instrument Co., Niles, Ill., Type 2545, wherein a ceramic head was cup-shaped and surrounded a thermocouple. The thermocouple extended slightly beyond the plane of the rim of the cup and was supported only by resilient conductor wires electrically connected to the thermocouple. The rim of the cup was adapted to be placed against the surface of the object the temperature of which was to be measured, and the ceramic head had a slightly loose connection with the shank of the hand-held probe. Again, this prior art construction had a deficiency that the resilient thermocouple wires were flexed as the temperature-sensing probe was pressed against the object surface, again causing repeated flexing which could result in breakage of the thermocouple wires.